JP2006526234A - Copy window constant control for domain expansion reading - Google Patents

Abstract

The present invention relates to a recording medium, a calibration method, and a reading device that reads the recording medium. The size of the spatial copy window of the domain copy process is varied according to the control information derived from the read pulse and at least one predetermined read parameter is changed to a predetermined additional change pattern of a predetermined parameter. Control by applying. A characteristic value (for example, phase amplitude) of the phase change induced in the reproduction data pattern by the additional change pattern is used as a reference set point for copy window control. Determining a predetermined optimum value of at least one predetermined parameter and monitoring the data pattern reproduced by the reading device in order to detect a characteristic value of the induced phase change when the optimum value of the reading parameter is applied To do. As another means, the feature value may be stored in a recording medium. This provides a set point signal that can be measured accurately. Furthermore, if the set point is stored as an intrinsic characteristic of the recording medium, the number of calibration operations can be greatly reduced.

Description

Detailed Description of the Invention

  The present invention relates to a recording medium such as MAMMOS (Magnetic Amplifying Magneto-Optical System), a calibration method, and an apparatus for reading the recording medium. The recording medium has a recording or storage layer and an expansion or reading layer. The copy window is dynamically controlled by changing predetermined read parameters according to control information obtained from the read pulse.

  In conventional magneto-optical storage systems, the minimum width of a recorded mark is determined by the diffraction limit, that is, the numerical aperture of the focusing lens and the laser wavelength. In order to reduce the width, generally, the laser wavelength is shortened and the numerical aperture of the focusing optical system is increased. At the time of magneto-optical recording, the minimum bit length can be made smaller than the optical diffraction limit by using laser pulse magnetic field modulation (LP-MFM). In LP-MFM, bit transitions are determined by magnetic field switching and temperature gradients induced by laser switching.

  In the domain expansion method such as MAMMOS, when heated by a laser, a write mark having a size smaller than the diffraction limit is copied from the storage layer to the readout layer by an external magnetic field. Since this readout layer has low holding power, the copied mark spreads over the entire light spot, and a saturated signal level can be detected regardless of the mark size. When the external magnetic field is reversed, the expanded domain disappears. On the other hand, the storage layer space is not copied and does not expand. Therefore, no signal is detected in this case.

In order to read the bits and domains of the storage layer, the thermal profile of the light spot is used. When the temperature of the read layer is higher than a predetermined threshold, the magnetic domain is copied from the storage layer to the magnetostatically coupled read layer. This is because the stray magnetic field Hs from the storage layer (proportional to the magnetization of the storage layer) increases as a function of temperature. In the temperature region immediately above the compensation temperature Tcomp, the magnetization Ms rises as a function of temperature. This feature is attributed to the occurrence of two opposing magnetizations M _RE (rare earth component) and M _TM (transition metal component) in the opposite directions because the rare earth transition metal (RE-TM) alloy was used.

  When an external magnetic field is applied, the copied domain of the readout layer is expanded, and a saturation detection signal can be obtained regardless of the size of the original domain. The copy process is very non-linear. When the temperature is above the threshold, the magnetic domain is coupled from the storage layer to the read layer. The following conditions are met at temperatures above the threshold.

Hs + Hext ≧ Hc (1)
Here, Hs is a stray magnetic field of the storage layer in the reading layer, Hext is a magnetic field applied from the outside, and Hc is a holding force of the reading layer. The space area where this copying occurs is called the “copy window”. The copy window size w is very important for accurate reading. If the condition (1) is not satisfied (copy window size w = 0), copying does not occur. On the other hand, if the size of the copy window is too large, it overlaps with surrounding bits (marks), and an additional “interference peak” is created. The size of the copy window depends on the shape of the temperature profile itself (ie the laser power itself, but also the ambient temperature), the strength of the external magnetic field, and the material parameters that vary over a narrow (or wide) range.

  The laser power used in the read process must be large enough for copying to occur. On the other hand, when the laser power is large, the overlap between the coercive force profile induced by temperature and the stray magnetic field of the bit pattern is increased. As the temperature increases, the holding force Hc decreases and the stray magnetic field increases. If this overlap becomes too large, the space can no longer be read correctly due to false signals caused by surrounding marks. The difference between the maximum laser power and the minimum laser power determines the power margin. The power margin is greatly reduced as the bit length is reduced. According to experiments, the current method can detect a bit length of 0.10 μm correctly, but the power margin is less than 1%. Therefore, when the density is maximized, the power margin becomes very narrow. Therefore, optical power control during reading is important.

  In MAMMOS, synchronization with the recording data of the external magnetic field is indispensable. Accurate clock recovery is possible by using data dependent magnetic field switching. Furthermore, at high density, the range of laser power that can be used for accurate readout becomes very narrow. However, an accurate power control loop (i.e., dynamic copy window control) can be created using the read signal from the recorded data by utilizing the sensitivity to the read laser power. For this purpose, a small modulation component is added to the laser power to induce a timing shift of the MAMMOS signal. In order to keep the copy window constant, any change in laser power, external magnetic field, ambient temperature can be corrected, for example, by detecting lock-in of these shifts. In this way, accurate and robust readout is possible even at a much higher density than conventional systems.

  Figure 2 shows some of the important MAMMOS disk readout signals in a steady state with constant laser power, constant ambient temperature, uniform disk characteristics, constant magnetic field strength, and constant coil-disk distance. Yes. The top graph shows the magnetic bits of the storage layer. The second graph shows the overlapping signal (convolution) of the magnetic bit pattern and the copy window. The third graph shows the external magnetic field and the bottom graph shows the acquired MAMMOS signal. When the overlap signal is not zero, domain copying occurs. A strong external magnetic field is maintained until a bit or domain is copied from the storage layer and expanded (shown in bold in FIG. 2) in the readout layer. After a certain delay, the external magnetic field is reversed and the domain is erased until the next bit transition or domain copy occurs.

  FIG. 3 is a diagram similar to FIG. 2, but one of the control parameters such as laser power is intentionally increased, for example, by the dynamic copy window control function described above. This increase / decrease (wobbling) is performed in a predetermined change pattern such as a periodic pattern with a small amplitude. By wobbling, the size of the copy window increases or decreases in synchronization with the wobble period. Comparing FIG. 2 and FIG. 3, the following becomes clear. That is, as the size of the copy window increases, the next transition appears a little earlier than expected. On the other hand, if the size of the copy window is reduced, the next transition is slightly delayed. This is indicated by the phase error amplitude ΔΦ shown in FIG.

  The upper part of FIG. 4 shows an outline of the dependence of the copy window size on the readout parameter x (ie laser power and / or external magnetic field). When the read parameter is modulated with the amplitude Δx, the copy window size also shows a change Δw correspondingly. As a result, as shown in the lower part of FIG. 4, the phase change directly occurs with the amplitude ΔΦ. This phase amplitude ΔΦ is a direct metric of the read parameter due to the non-linear square root dependence of the copy window size w on the read parameter x. In order to determine the absolute value of the error signal used as an input to the copy window control loop, the present control method requires a suitable reference set point corresponding to the optimal readout parameters such as external magnetic field and / or laser power. However, no method for determining and calibrating this set point has been proposed so far. A suitable set point may be found using a calibration method. However, this takes time and increases startup time.

  One of the objects of the present invention is to provide a readout system and calibration method that can determine a suitable reference set point and can be easily calibrated. This object can be achieved by the method according to claim 1, the device according to claim 13, and the record carrier according to claim 20.

  Therefore, using the characteristic value of the phase change signal corresponding to the optimum readout parameter as a reference point, this value is independent of temperature change and lock-in detection of the output of the phase detector of the clock recovery phase lock loop Makes it possible to measure very easily and accurately. Thus, almost no changes to the hardware are necessary.

  Furthermore, unnecessary calibration can be eliminated by alternative or additional means of storing this set point on the recording medium. The set points can be preset at the factory and, as suggested above, need to be updated at the reader by calibrating if a read problem occurs (eg non-standard player, disc aging, etc.) Only.

  The at least one limit value includes a lower limit value determined by occurrence of at least one lost peak of the reproduction data pattern and an upper limit value determined by occurrence of at least one false peak of the reproduction data pattern. But you can. In particular, the predetermined value may be a value between the upper limit value and the lower limit value, for example, a value approximately in the middle between the upper limit value and the lower limit value.

  Furthermore, the predetermined readout parameter may correspond to at least one value of the radiation power and the external magnetic field.

  The additional change pattern may be a periodic modulation pattern having a predetermined frequency.

  The monitored reproduction data pattern may be a predetermined and known data pattern provided in the calibration area of the recording medium. Thereby the amount of data analysis can be minimized. As an alternative, the monitored reproduction data pattern may be any user data pattern provided in the recording area of the recording medium, and the determining step may be based on run-length violation detection.

  At least one predetermined readout parameter is passively swept from a low value to a high value or vice versa during the changing step. The lower value is lower than all possible values of the lower limit, and the higher value is higher than all possible values of the upper limit.

  Alternatively, the at least one predetermined read parameter may be actively changed from an initial default value to a lower or higher value during the changing step. The direction of change depends on the number of false or missing peaks determined in the playback data pattern during the monitoring step.

  In any case, when the number of lost peaks detected during the monitoring step reaches a predetermined first threshold, a lower limit is set to a value corresponding to the lower value, and the monitoring step When the number of false peaks detected at the time reaches a predetermined second threshold, an upper limit value is set to a value corresponding to the higher value.

  The use of information about lost or false peaks is based on detecting the difference between the detected peak and the expected peak, thus providing quick and easy control feedback.

  The calibration means of the readout device determines a predetermined optimum value of at least one predetermined parameter and, when the optimum value of the readout parameter is applied, detects the characteristic value of the induced phase change by the readout device. Monitor the replayed data pattern.

  As another or additional means, the readout device is calibrated to read the feature values from the recording medium and supply the feature values to the calibration means. In particular, the reading device is calibrated to read out the characteristic values from the recording medium based on at least one predetermined parameter of the recording medium. The at least one predetermined parameter of the recording medium may include at least one of a radial position and a read speed. Of course, the stored feature values are read according to other parameters of the recording medium that affect the feature values. Thus, the feature value is treated as an intrinsic characteristic of the recording medium and can be preset during production.

  The calibration information stored on the recording medium determines a plurality of set points for different values of at least one parameter of the record carrier.

  Other advantageous alternative embodiments are described in the dependent claims.

  Hereinafter, the present invention will be described based on preferred embodiments with reference to the accompanying drawings.

  A preferred embodiment will be described based on the MAMMOS disc player shown in FIG. FIG. 1 is a schematic diagram showing the configuration of a disc player according to a preferred embodiment. The disc player has an optical pickup unit 30 having a laser light emitting section and a magnetic field applying section. The laser light emitting section irradiates a magneto-optical recording medium such as a magneto-optical disk or a record carrier 10 with light converted into pulses during reading in a pulse cycle synchronized with code data. The magnetic field application section has a magnetic head 12 that applies a magnetic field in a controlled manner during recording and reproduction to the magneto-optical disk 10. In the optical pickup unit 30, the laser is connected to a laser drive circuit, and the laser drive circuit receives recording and reading pulses from the recording / reading pulse adjustment unit 32, and laser pulses of the optical pickup unit 30 during recording and reading operations. Control amplitude and timing. The recording / reading pulse adjustment circuit 32 receives a clock signal from a clock generator 26 having a PLL (phase lock loop) circuit.

  It should be noted that the magnetic head 12 and the optical pickup unit 30 are shown on the opposite side of the disk 10 in FIG. 1 for simplicity. However, in the preferred embodiment, they are located on the same side of the disk 10.

  The magnetic head 12 is connected to the head driver 14 and receives data subjected to code conversion from the modulator 24 via the phase adjustment circuit 18 during recording. The modulator 24 converts the input recording data DI into a predetermined code.

  During reproduction, the head driver 14 receives a timing signal from the timing circuit 34 via the reproduction adjustment circuit 20. The reproduction adjustment circuit 20 generates a synchronization signal for adjusting the timing and amplitude of the pulse applied to the magnetic head 12. The timing circuit 34 obtains a timing signal from the data read operation. Therefore, magnetic field switching depending on the data can be performed. A recording / reproducing switch 16 is provided to switch or select a signal supplied to the head driver 14 during recording and reproduction.

  Furthermore, the optical pickup unit 30 has a detector that detects the laser beam reflected from the disk 10 and generates a corresponding read signal. The read signal is input to the decoder 28. Decoder 28 decodes the read signal to generate output data DO. Furthermore, the read signal generated by the optical pickup unit 30 is supplied to the clock generator 26. The clock generator 26 extracts or recovers the clock signal obtained from the embossed clock mark of the disk 10 and supplies the clock signal to the recording pulse adjustment circuit 32 and the modulator 24 for synchronization. In particular, the data channel clock is generated by the PLL circuit of the clock generator 26. Alternatively, the clock signal obtained from the clock generator 26 is supplied to the regeneration adjustment circuit 20 to provide reference or fallback synchronization. This synchronization supports data dependent switching or synchronization controlled by the timing circuit 34.

  In the case of data recording, the laser of the optical pickup unit 30 is modulated at a fixed frequency corresponding to the cycle of the data channel clock, and the data recording area or spot of the rotating disk 10 is locally heated at an equal distance. The data channel clock supplied by the clock generator 26 controls the modulator 24 to generate a data signal every standard clock period. The recording data is modulated and code-converted by the modulator 24 to obtain binary run length information corresponding to the information of the recording data.

  The configuration of the magneto-optical recording medium 10 may correspond to the configuration described in Japanese Patent Publication No. 2000-260079.

  In FIG. 1, a timing circuit 34 is provided to supply a data-dependent timing signal to the reproduction adjustment circuit 20. Alternatively, data-dependent switching of the external magnetic field is achieved by supplying a timing signal to the head driver 14 to adjust the timing or phase of the external magnetic field. Timing information is obtained from (user) data on the disk 10. For this reason, the reproduction adjustment circuit 20 or the head driver 14 is configured to generate an external magnetic field (usually in the enlargement direction). When the timing circuit 34 captures the rise of the MAMMOS peak signal in the input line connected to the output of the optical pickup unit 30, the timing signal is supplied to the reproduction adjustment circuit 20, and the head driver 14 is controlled to expand the expanded domain of the readout layer. In order to erase, the magnetic field is reversed after a short time. Shortly thereafter, the magnetic field is reset in the expansion direction. The time between peak detection and magnetic field reset is set by the timing circuit 34 and corresponds to the maximum allowable copy window of the disk 10 and the sum of the 1 channel bit length (multiplied by the disk linear velocity).

  Furthermore, a dynamic copy window is obtained by modulating the laser power control signal (eg, wobble or pattern change) and continuously measuring the copy window size w using information from the data signal detected in the read mode. Provide a control function. When the wobble frequency is higher than the bandwidth of the clock recovery PLL circuit of the clock generator 26, the phase error of the PLL circuit can be used to detect a small deviation or phase error related to the expanded transition position.

  The average frequency deviation of the introduced wobble or pattern change should be zero. However, the phase error amplitude ΔΦ obtained here cannot be directly used as an absolute value error signal for laser power control. This is because the absolute scale is known but there is no reference (zero or offset). That is, only the change in the copy window size can be measured. In order to avoid this problem, the derivative of the copy window size is measured as a function of temperature, and control information for controlling the copy window size w is obtained. Since the phase amplitude ΔΦ can be directly obtained from the derivative or change amount of the copy window size w, the detected phase error amplitude ΔΦ coincides with the derivative and can be specified for the control of the copy window. As a reference condition, this phase error amplitude ΔΦ must satisfy the initially determined setpoint or setpoint. The control signal PE can be used to control the displacement from this set point for laser power control methods, or other suitable readout parameters (eg, the strength of the external magnetic field).

  For the controlled parameter (for example, laser power in this embodiment), a change in copy window size due to a change in parameters such as coil-disk distance and environmental temperature is compensated.

  However, the w vs. x curve shown in FIG. 4 shifts in the horizontal direction according to the environmental temperature. For example, if the temperature in the drive changes during operation, it is not sufficient to only store the “optimal” value of the laser power and the external magnetic field. These “optimal” values are different at different temperatures. Furthermore, measuring the absolute values of these values in the drive is not easy. Detectors and probes used for this purpose are prone to drift and require calibration. According to a preferred embodiment, it has been proposed to use the phase amplitude corresponding to the optimum readout parameter as a reference point. This value does not depend on temperature change and can be measured very easily and accurately by detecting the lock-in of the output of the phase detector in the clock recovery PLL circuit of the clock generator 26.

  FIG. 5 is a view similar to the lower part of FIG. 4 and shows a range of read parameters for correct reading between x1 and x2. x1 is the lower limit of the correct read parameter, and x2 is the upper limit. For example, in the lower forbidden area 101, the laser power is less than x1 and the mark run length produces fewer MAMMOS peaks than expected. Similarly, in the upper forbidden area 102, the laser power is higher than x2, resulting in an additional false peak.

  FIG. 6 is a flow diagram illustrating a calibration method according to a first preferred embodiment. In the proposed calibration method, in step S201, the readout parameters are changed while monitoring and analyzing the reproduction data pattern, and the limits x1 and x2 are determined. No modulation Δx is applied and the window control loop is not closed. That is, copy window control is not active. Next, in step S202, the read parameter is set to a value between x1 and x2, preferably about (x1 + x2) / 2. In subsequent step S203, a fixed modulation Δx is applied as in the case where the control loop is active, and the corresponding phase amplitude ΔΦ is measured. The measured phase amplitude ΔΦ is used as a new set value SP. A new setpoint SP can be used to (again) activate the copy window control loop.

  In the disc player shown in FIG. 1, a corresponding configuration circuit 290 configured to determine the set value SP of the clock generator 26 is provided. According to a first preferred embodiment, this setpoint is determined using the calibration procedure of FIG. Alternatively or in addition, according to the second preferred embodiment, the setting value SP may be stored in advance on the disk and read out and supplied to the calibration circuit 290.

  FIG. 7 is a detailed functional block diagram showing a copy window control function using the control signal of the calibration circuit 290. Blocks 261 to 265 constitute a PLL unit, and blocks 274 to 276 constitute a lock-in detection function. That is, when the modulation frequency is applied to the signal, the sum and difference frequencies appear, and when a low-pass filter is subsequently applied, a DC value is obtained. That is, it is equivalent to lock-in. The corresponding configuration control signal of the first preferred embodiment is indicated by a dotted line.

  Similarly, a block diagram can show how to control the copy window based on modulation of an external magnetic field or a combination of a laser and a magnetic field. The control signal PE is supplied to the head driving unit 14 in addition or only.

  7, the MAMMOS run length signal acquired from the pickup unit 30 in FIG. 1 is supplied to the phase detector 261 of the PLL circuit of the clock generator 26 in FIG. The phase of the run-length signal is compared with the phase of the output signal of the voltage controlled oscillator (VCO) 263 of the PLL circuit. In addition, a feedback signal is provided to the clock divider 275. The clock divider 275 divides the clock frequency and supplies it to the modulation circuit 279 that modulates the laser power. The output of the phase detector 261 corresponds to the phase difference between the run-length signal and the feedback signal, and is supplied to the loop filter 262, where a desired frequency is extracted and phase-controlled by the PLL circuit.

  Due to the data dependent magnetic field switching, the high frequency component of the phase error from the phase detector 261 includes the pulse position of the reproduced data. When the laser power is modulated at a frequency M times lower than the bit clock, the phase error from phase detector 261 includes synchronous, low frequency laser power error information demodulated by demodulation or mixing circuit 274. The laser modulation signal output from the clock divider 275 is supplied to the demodulation or mixing circuit 274 and extracted using the low-pass filter 276. The combination of the mixing circuit and the low pass filter is equivalent to a band pass filter around the modulation frequency (ie, “lock-in” detection). The extracted phase error signal is supplied to the addition circuit 272, and the set value SP is added. The obtained total value is used as a control signal PE for power control. The control signal PE is supplied to an average circuit 280 (eg, a filter or an integration circuit) to obtain an average power control signal ALP. Another averaging circuit 278 adds this average power control signal ALP to the laser power modulation signal. The combined power control signal is supplied to the laser diode of the pickup unit 30 via the drive amplifier 277.

  The recovered output clock is also supplied to the bit detector 264. The bit detector detects the presence / absence of a bit in the output signal of the phase detector 261. The detected bit information is output as output data DO. This output data DO is supplied to the magnetic field switching control unit 265 together with the recovered output clock, and generates a magnetic field by controlling the coil driver 271 of the magnetic field coil of the magnetic head 12. In this way, the data dependent magnetic field switching function is implemented.

  Laser modulation shifts the pulse position in accordance with the sign of the modulation, as shown in FIG. This means that there is no longer a DC component in the average pulse position during the subsequent low period and the subsequent high period.

  With different approaches, x1 and x2 (step 201 in FIG. 6) by the configuration circuit 290 can be determined. Data analysis is minimized by a calibration area with a base data pattern provided on the disk 10. This is because the deviation in the number of detected peaks (for example, when the value below x1 is too small or the value above x2 is too large) is cleared immediately. User data calibration is possible in principle, but strong run-length violation detection requires special attention and longer data sequences, and the calibration procedure is time consuming. Therefore, the calibration pattern is preferably fixed.

  Changes in readout parameters (eg, laser power LP and / or magnetic field amplitude FA indicated by dotted arrows in FIG. 7) in calibration circuit 290 may be passive or active. If passive, the parameters are swept from bottom to top or vice versa while analyzing the playback data. Depending on the accuracy required, the sweep may be continuous or stepped. The lower value must be lower than x1 and the upper value must be higher than x2. That is, sweep all allowable temperature and disk characteristics. When a transition from “too few peaks” to “OK” or a reverse transition is detected during the sweep, the read parameter value at that time is stored in x1. As soon as a transition from “OK” to “too many peaks” or a reverse transition in the case of a sweep from top to bottom is detected, it is stored in x2.

  As an example of an active approach in which the readout parameter changes depending on the detection data, for example, a preset value may be started. The preset value may be determined in advance and set for the read parameter when the disk 10 is manufactured. Depending on the playback data, i.e., if there are too few peaks, OK, or too many peaks, a transition is detected and the parameter is increased continuously or stepwise until either x1 or x2 is stored or Decrease. The method is then repeated to find the second transition. For example, when the starting point is smaller than x1, x is increased and x1 is detected, and then x is further increased to x2. Similarly, when x is decreased, if the starting point is greater than x2, x is further decreased to x1 after x2.

  The proposed calibration method allows the setpoint signal to be accurately determined using existing hardware and a calibration method to optimal readout parameters.

  Since the difference between the number of peaks actually detected and the number of predicted peaks is a (non-linear) measure of deviation from the optimal readout parameter, this information can be used to coarsely correct the readout parameter value.

  In the case of RF-MAMMOS, since the external magnetic field is changed at a high frequency, it is important to control the copy window with a practical margin when the density is high. As suggested above, the phase amplitude induced by readout parameter modulation is a preferred set point and can be found by the simple calibration method described in connection with the first preferred embodiment. However, this correction method takes a little time and increases the startup time. In addition, such setpoints vary as a function of disk radius due to disk configuration non-uniformity and linear velocity differences, resulting in different temperature profiles and needing to be readjusted during playback. I understand.

  According to FIG. 4, the relationship between the fixed modulation of the readout parameter with the amplitude ΔΦ and the resulting copy window change ΔΦ and the corresponding phase amplitude ΔΦ is expressed in terms of the copy window size x to the readout parameter x. Depends entirely on dependencies. The shape of the curve shown at the top of FIG. 4 is determined by the temperature profile induced in the disk 10 and its magnetic characteristics, mainly the coercive force versus temperature characteristics of the readout layer. The horizontal shift occurs due to the effects of ambient temperature and external magnetic field, but the shape of the curve does not change. Therefore, the optimum read parameter changes due to the shift, but the phase amplitude set value SP always coincides with the optimum value of the read parameter.

  The temperature profile is determined by the optical system (that is, the laser wavelength and the numerical aperture of the objective lens) and the linear velocity of the disk. These are standardized and the specifications are determined accurately. The temperature profile is also determined by the layer structure of the disk. This means that the set value SP of the phase amplitude can be treated as an intrinsic characteristic of the disc.

  Therefore, in the second preferred embodiment, the disk 10 is set to this setting and another setting for at least one of the radius, speed, or other suitable disk parameters that affect the setting, or the disk 10 It is suggested to store / update another setpoint and only perform calibration if an unexpected problem occurs. This avoids unnecessary calibration. The setpoint SP can be preset in advance during production of the disc 10, for example as described in the first preferred embodiment (eg when using a non-standard player or when the disc has become stale Sometimes it only needs to be updated in the disc player by performing a calibration if a read problem occurs.

  Since the magnetic characteristics greatly depend on the layer structure and it is difficult to make the radial direction strictly uniform, it is preferable to store different set values at different radial positions or ranges thereof. Such an approach is useful for determining different setpoints for different linear velocities and speed ranges when operating at each speed constant (CAV) or zone CAV.

  According to a second preferred embodiment, the calibration circuit 290 is configured to obtain default or preset settings from the disk 10 based on the initial read operation. When there are a plurality of set values, the calibration circuit 290 is calibrated so as to select the current dominant set value SP according to the disk characteristics such as the radial position and each speed.

  It should be noted that the present invention can be applied to any read system of a magneto-optical disk storage system compatible with domain expansion using a copy window control function. Any suitable readout parameters will change during calibration to obtain the optimal setpoint SP. Furthermore, any suitable change pattern may be applied to the selected readout parameters to derive an upper limit value x1 and a lower limit value x2, or more values, or a single value. Based on this, the optimum set value SP can be obtained. The calibration circuit 270 may be implemented by hardware or software controlled analog or digital processing circuitry, and may be incorporated as a new routine in an existing control program that controls the disc player. Thus, the preferred embodiments may vary within the scope of the appended claims.

1 is a schematic diagram illustrating a magneto-optical disk player according to a preferred embodiment. FIG. It is a figure which shows the characteristic signal of the MAMMOS read-out method with respect to predetermined fixed copy window size. It is a figure which shows the characteristic signal of the MAMMOS reading method which enlarged the copy window size in which the timing shift of the detected MAMMOS peak occurs. It is a figure which shows the dependence between a predetermined read parameter, a copy window size, and a phase change. It is a figure which shows the allowable change range of a read parameter. FIG. 3 is a flow diagram illustrating a calibration method according to a first preferred embodiment. FIG. 3 is a schematic block diagram illustrating a copy window control circuit having a calibration function according to first and second preferred embodiments.

Claims (26)

A calibration method for calibrating a copy window control set point during reading of a magneto-optical recording medium having a storage layer and a reading layer, comprising:
By copying a mark area from the storage layer to the readout layer when heated by radiant power using the external magnetic field, an expanded domain that produces a readout pulse is generated in the readout layer,
The method
a) changing at least one predetermined read parameter;
b) monitoring the data pattern reproduced during the changing step;
c) determining at least one limit value of the at least one predetermined read parameter based on the monitored data pattern;
d) setting the at least one readout parameter to a predetermined value determined based on the limit value;
e) applying a predetermined further change pattern to the predetermined parameter;
f) using as a control setpoint a feature value of a phase change induced in the reproduced data pattern by the further change pattern. The method of claim 1, comprising:
The at least one limit value is determined by a lower limit value determined by losing at least one peak in the reproduced data pattern and the appearance of at least one false peak in the reproduced data pattern. And having an upper limit.   3. A method according to claim 1 or 2, wherein the feature value corresponds to an amplitude of the phase change. The method of claim 2, comprising:
The method according to claim 1, wherein the predetermined value is between the lower limit value and the upper limit value. A method according to any one of claims 2 to 4, comprising
The method is characterized in that the predetermined value is approximately in the middle of the lower limit value and the upper limit value. A method according to any one of claims 1 to 5, comprising
The method according to claim 1, wherein the predetermined readout parameter corresponds to at least one of the value of the radiation power and the value of the external magnetic field. A method according to any one of claims 1 to 6, comprising
The method according to claim 1, wherein the further change pattern is a periodic modulation pattern having a predetermined frequency. A method according to any one of claims 1 to 7, comprising
The method of claim 1, wherein the reproduced data pattern is a predetermined data pattern provided in a calibration area of the recording medium. A method according to any one of claims 1 to 7, comprising
The reproduced data pattern is an arbitrary user data pattern provided in a recording area of the recording medium,
The method of determining, wherein the determining step is based on detecting run length violations. A method according to any one of claims 1 to 9, comprising
The at least one predetermined readout parameter is passively swept from a low value to a high value or vice versa during the changing step, the low value being lower than all possible values of the lower limit value, The high value is higher than all possible values of the upper limit value. A method according to any one of claims 1 to 9, comprising
The at least one predetermined readout parameter is actively changed from an initial default value to a lower or higher value during the changing step, and the direction of change is reproduced during the monitoring step. A method characterized in that it depends on the number of false or missing peaks determined in the data pattern. 12. The method according to claim 10 or 11, comprising:
The lower limit is set to a value corresponding to the lower value when the number of lost peaks detected during the monitoring step reaches a predetermined first threshold, and the upper limit is set to the monitor A method, wherein the number of false peaks detected during the step of setting is set to a value corresponding to the high value when a predetermined second threshold value is reached. A reading device for reading a magneto-optical recording medium having a storage layer and a reading layer,
By copying a mark area from the storage layer to the readout layer when heated by radiant power using the external magnetic field, an expanded domain that produces a readout pulse is generated in the readout layer,
The device is
Control means for controlling the size of the spatial copy window of the copy process by changing at least one predetermined read parameter in response to control information derived from the read pulse;
Changing means for applying a predetermined further change pattern to the at least one predetermined parameter;
Calibration means using a characteristic value of the phase change induced in the reproduction data pattern by the further change pattern as a reference set value of the control means;
A reading device comprising: The reading device according to claim 13,
The calibration means determines a predetermined optimal value of the at least one predetermined parameter and detects the characteristic value of the induced phase change when the optimal value of the readout parameter is applied. A reading device that monitors the data pattern reproduced by the reading device. The reading device according to claim 13,
A reading apparatus calibrated to read out the feature value from the recording medium and to supply the feature value to the calibration means. The reading device according to claim 15,
A reading apparatus configured to read the feature value from the recording medium based on at least one predetermined parameter of the recording medium. The reading device according to claim 16, wherein
The reading apparatus characterized in that the at least one predetermined parameter of the recording medium has at least one of a radial position and a reading speed. A reading device according to any one of claims 13 to 17,
The reading device according to claim 1, wherein the characteristic value corresponds to an amplitude of the phase change. A reading device according to any one of claims 13 to 18, comprising:
A reading device characterized by being a disc player for a MAMMOS disc. A recording medium having a storage layer and a readout layer,
By copying a mark area from the storage layer to the readout layer when heated by radiant power using the external magnetic field, an expanded domain that produces a readout pulse is generated in the readout layer,
The recording medium is written with calibration information for determining a reference set point for controlling a size of a spatial copy window of the copy process. The recording medium according to claim 20, wherein
A recording medium, wherein the calibration information determines a plurality of reference set points for different values of at least one parameter of the recording medium. The recording medium according to claim 21, wherein
The recording medium, wherein the at least one predetermined parameter of the recording medium has at least one of a radial position and a reading speed. A recording medium according to any one of claims 20 to 22,
The recording medium, wherein the feature value corresponds to a phase amplitude of a data pattern reproduced from the recording medium. A recording medium according to any one of claims 20 to 23, wherein
A recording medium having a calibration area having a predetermined data pattern for calibration of the reference set point. A recording medium according to any one of claims 20 to 23, wherein
The recording medium further comprising a calibration area having an arbitrary user data pattern for calibration of the reference set point. A recording medium according to any one of claims 20 to 25, wherein
A recording medium characterized by being a MAMMOS disk.

Images